The indentation fracture toughness (KC) and its parameters: the case of silica-rich glasses

The fracture toughness of several glasses, including soda-lime-silica and aluminosilicate glasses, was measured by both the indentation fracture (IF) and the single-edge notched beam (SENB) techniques. The flow densification mechanism occurring during indentation for silica-rich compositions leads to discrepancies between the two methods. The influence of the indentation load and the post-indentation fatigue duration on the indentation on the crack length and on the fracture toughness measurement were investigated. Fatigue curves (V–K) were obtained directly from indentation experiments and fatigue parameters were derived. The sub-critical crack growth resistance was found to be improved by increasing the silica content. In comparison with the studied oxide glasses, a Y-SiAlON oxynitride glass exhibits much greater fatigue resistance. The fatigue phenomenon has a major effect on the estimation of KC from indentation-cracking measurements.